Async MessageObject

I am trying to use Fetch.BeginMessageObject method to get a message object but the state object that I receive in my callback method is of type DelegateMessageObject (which I do not know what to do with). My callback method looks like this:
public void callBack(IAsyncResult result)
{

// result.AsyncState is of type DelegateMessageObject

}

Is there anyone having a working example of an async method call of this library?